1. Field of the Invention
This invention relates to a highly sealed self-lubricating linear guide apparatus, and more particularly, to a self-lubricating linear guide apparatus which can automatically lubricate rolling elements in the unloaded rolling passages of a linear guide with the lubricant stored in the slider while the slider is moving, and its lubricating function may last through the whole life time of the linear guide.
2. Description of the Prior Art
Two examples of conventional manual-lubricating linear guide apparatuses are shown in FIG. 1, 2 and 3. It is well known that a linear guide consists of an endlessly extendable guide rail 1 and a slider 2 is composed of a slider body 3 and end caps 4 attached to both ends of the slider body 3 which moves along the guide rail 1. Inner passages 9 in the slider body 3 and the inner return passages 10 provided in both end caps 4 form unloaded rolling passages,and guide rail rolling grooves 11a, and rolling grooves for slider 11b (The grooves are arc shaped if rolling elements are steel balls as shown in FIGS. mentioned above, if rolling elements are rollers, the shape of the grooves is linear) constitute loaded rolling grooves. Unloaded rolling passages and loaded rolling grooves constitute circulation passages 12. A certain numbers of rolling elements 8 are employed in the circulation passages 12 for endlessly circulating motion. The slider 2 moves with a low friction resistance along the guide rail 1 by means of the rolling elements 8. A lubrication passage 13 is formed in each end cap 4 attached to the slider body 3. Lubricant grease can be charged therein with an grease gun 7 through a grease nipple 6 fixed to the side of an end cap 4. Incidentally, the lubricant grease flows into the circulation passage 12 along the lubrication passage 13 so as to lubricate the rolling elements 8. Alternatively, as shown in FIG. 3, an oil pipe 7 from an automatic lubrication system is connected to an oil-pipe joint 6 provided at the side of an end cap for supplying the lubricant to the rolling elements 8 via the lubricant passage 13 in a fixed time interval. However, the two lubrication methods mentioned above have a common shortcoming that the sealing effect for lubricant has been too poor. Leakage of more than 95% lubricant is inevitable which causes not only loss of operation cost but also contamination of surroundings. In addition, large amount of lubricant loss causes shortage of lubrication for linear guide in long distance application. As a result, the life of a linear guide will be severely shortened. Therefore, for prolonging the life of linear guide, the lubricant must be replenished frequently.
There was recently a comparatively improved technique in this field disclosed by U.S. Pat. No. 5,615,955 shown as FIG. 4. In this cited case lubricant containing polymer spacer balls 14 of smaller diameter then that of steel balls are employed together with circulating steel balls 8 spacing with each other. When the slider moves the polymer spacer balls 14 can exude their containing lubricant to lubricate adjacent rolling steel balls 8 by mutual friction therebetween. However, the most disadvantageous shortcoming of this design is that the available amount of steel balls will be reduced to about half as many as that without using polymer spacer balls since some space is occupied by the latter. As a result, the load rating of the linear guide has to be reduced to 1/2 as large as that in the case full amount of steel balls are utilized.
FIG. 8 is a drawing illustrating an embodiment of this cited invention. A recessed groove 15 is provided for both the loaded rolling grooves 11b approximately at the half of unloaded portion and a strip shaped lubricant-containing polymer 14 is inserted in each recessed groove 15. This polymer 14 contacts with the rolling balls 8 tightly to impart its lubricant to the rolling balls 8 so as to lubricate the rolling balls 8. The lubrication effect is achieved by mutual contact between the rolling balls 8 and the lubricant containing polymer 14 during rotation of the balls 8. Incidentally, as soon as the lubricant containing polymer 14 is worn due to long time abrasion with the rolling balls 8, the mutual contact therebetween becomes incomplete, or in the worst case, becomes completely apart from each other. Accordingly, the lubrication effect for the linear guide apparatus is degraded. Further, as soon as the limited lubricant content in the polymer 14 is used up, no further lubrication effect can be expected for this system since the lubricant containing polymer can not be replaced, nor can the lubricant be replenished.
FIGS. 5 through 7 illustrate another recent invention patented by U.S. Pat. No. 5,857,779. Here, a lubricant containing polymer 14 is attached to each side of the slides. The outer appearance of this lubricant containing polymer 14 is such that a projected portion 14a is adjacent to the surface of rolling grooves 11a. When the slider 2 moves, the lubricant contained in the polymer 14 is exuded to lubricate the surface of the guide rail rolling grooves 11a. Furthermore, in another embodiment of this cited case shown in FIGS. 9 through 11, a lubricant containing member 14 is provided at each side of the slider. The figure of the member 14 resembles a end cap 4 with a hollow inner portion in which a material 14b with excellent oil absorbing property and full of lubricant oil is filled. A non-woven cloth 14a is placed near each end cap 4 for contacting with the surface of the guide rail rolling grooves 11a. When the slider 2 moves the non-woven cloth 14a continuously oozes the lubricant from the lubricant containing member 14 to lubricate the surface of the guide rail rolling grooves 11a through mutual contact. As soon as the rolling balls 8 come to the surface of the guide rail rolling grooves 11a, the rolling balls 8 can be lubricated with the lubricant thereon. However, such a design mentioned above has shortcomings. First, it is difficult to install the whole quantity of lubricant needed through the life time of the linear guide. Second, the slider becomes bulky and too long as it has to load a large amount of lubricant. Third, the surface of the linear guide apparatus is often contaminated with foreign material such as metallic powder, grains, dust or the like which greatly degrade the lubrication effect and shorten the life of the linear guide apparatus as well. Fifth, replenishment of lubricant is hard and sacrificing the operation time as the whole apparatus has to be detached and then reassembled. Sixth, the lubrication effect is insufficient since the rolling grooves for slider block is indirectly lubricated only by the lubricant carried by the rolling elements. Seventh, it is wasteful to form oil film on entire surface of the guide rail rolling grooves since the contact between the steel ball and the surface of the grooves is a point contact, thus too much lubricant will be wasted. In all, the two cited cases mentioned above utilize a lubrication method of direct lubricant supply by frictional contact between the lubricant containing media and the mechanical parts to be lubricated, therefore, there is a large frictional loss which lowers mechanical efficiency.